Crown caps



R. E. FORD CROWN CAPS June 4, 1963 Filed June 8, 1959 m Q m 5% United States Patent 3,092,280 CROWN CAPS Ralph Ewart Ford, Bedford, England, assignor to Fords (Finsbury) Limited, Bedford, England, a British com- Filed June 8, 1959, Ser. No. 818,753 Claims priority application Great Britain June 11, 1958 4 Claims. (Cl. 21540) The present invention relates to the closing and sealing of bottles by means of crown caps, and to improved crown caps for efiecting such closing and sealing. More particularly the invention relates to a crown cap made from aluminium or an aluminium alloy (hereinafter referred to as aluminium) which is suitable for closing and sealing a bottle containing a liquid under pressure, such as beer or an aerated mineral water, or a liquid which is heated after the crown cap has been applied in order to sterilise or pasteurise the contents of the bottle, such as sterilised milk or pasteurised fruit juice drinks.

The conventional crown cap in use to-day consists of a cap made of tinplate with a top portion and a corrugated skirt, the cap being fitted with a cork disc which, when the corrugated skirt is crimped beneath the rim flange or locking ring around the bottle neck, seals against the top of the bottle. In some instances the cork disc has been replaced by a disc or annulus of a resilient plastic material, such as polythene, which may be formed with annnular ridges on its surface for increasing the resilience of the seal against the top of the bottle. In other instances the inside of the top of the cap has been covered entirely with, or only partly by an annulus of, a flowed-in resilient sealing compound which adheres firmly to the underside of the top portion of the cap and is compressed against the top of the bottle when the corrugated skirt is crimped around the rim flange.

Since the existing crown caps achieve sealing by the cork disc or sealing gasket being pressed against the top of the bottle neck, any lifting or doming of the crown cap under the gas pressure within the bottle tends to produce leakage. Therefore, when crimping existing caps on to a bottle, the cap is always pressed down on to the bottle with a heavy pressure (a pressure of 600 lbs. is normal) in order to compress the cork disc or sealing gasket to a considerably reduced thickness and thereby effect and maintain a gas-tight seal. Where the sealing gasket is formed of a flowed-in sealing compound, the compound is generally located in a recess or channel formed around the periphery of the underside of the top portion of the cap in order to prevent the compound from plastically flowing away from the sealing position under the applied sealing pressure.

The present invention has for its object to provide a crown cap having a sealing gasket which is so disposed in and assembled to the metal cap that the gas pressure within the bottle acts on the sealing gasket to maintain the tightness of the seal.

The present invention consists in a crown cap made of metal, preferably aluminium, having a top portion and a corrugated skirt portion which is adapted to be crimped on to the rim flange around the neck of a bottle, said cap having an annular sealing gasket of a resilient or deformable sealing compound, such as a rubberised compound, applied around the interior of the corner Zone of the cap between the top portion and the skirt portion, wherein the sealing gasket, the internal diameter of which is greater than the diameter of the bore of the neck of the bottle, does not firmly adhere to the interior of the cap and is adapted, under the internal gas pressures exerted thereon after the cap has been secured on the bottle, to move or deform by sliding or slipping of the compound against the top and skirt portions of the cap and thereby to effect self-sealing of the cap on the bottle.

According to a feature of the invention, the compound is applied on to a coating, previously applied on the interior surface of the cap, of a material to which the compound does not adhere.

When a crown cap according to this invention is crimped on to a bottle, the ring of sealing compound is compressed against the upper peripheral zone of the rim flange, and by reason of the compound not adhering to the cap, the gas pressure within the bottle can move the compound to effect sealing of any spaces which might exist after crimping or which may be produced by any lifting or doming of the cap due to any increased pressure which may subsequently be produced in the bottle. The cap is thus self-sealing and does not have to be sealed on the bottle with the application of such a heavy downward pressure on the bottle neck as is necessary with conventional crown caps.

The invention also consists in the methods of making crown caps as hereinafter described.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, in which:

FIGURE 1 is a perspective view from above of a crown cap according to the invention,

FIGURE 2 is a perspective view from below of the cap of FIGURE 1,

FIGURE 3 is a section through a bottle neck with the cap in position thereon, showing the cap before crimping,

FIGURE 4 is a similar section showing the cap after crimping on to the bottle,

FIGURE 5 is a section through a bottle neck having a cap of modified construction sealed thereon, before crimping,

FIGURE 6 is a similar view to FIGURE 5 but showing the cap after crimping.

Referring .to FIGURES 1 to 4 of the drawings, the cap 1 is punched from sheet or strip aluminium (such as the aluminium alloy known as BAZl supplied by British Aluminium Ltd. or the alloy known as 578 supplied by Northern Aluminium Ltd.), conveniently of about .3 mm. thickness, and is formed to provide the top portion 2 and the downwardly depending corrugated ski-rt portion 3, the edge part 4 of the skirt being flared outwardly. Around the internal surface of the cap, in the zone of the corner between the top portion 2 and the skirt portion 3 there is applied, in a semi-liquid state, a ring 5 of a resilient or deformable sealing compound, preferably a rubberised compound. The compound may be flowed-in from a nozzle while rotating the cap. The compound is then solidified, for example by heating which may also effect any vulcanisation which may be necessary, to form an annular sealing gasket. A suitable sealing compound is No. G485 marketed by Dewey and ALmy Limited.

The compound is applied either directly on to the sur face of the aluminium or on to a coating which has been previously applied on the inner surface of the cap, the coating being such that the sealing compound does not stick thereto. Suitable non-adhesive coatings for the above-mentioned compound are lacquers made from epoxy-phenolic resins. In either case the sealing compound does not stick or firmly adhere to the cap, although when the compound is dry, the close surface contact between the sealing gasket and the surface on which it is applied produces sufficient suction between the gasket and the cap to hold the gasket in position in the cap during the application of the cap to a bottle to be sealed and during any hoppering .to which the cap may be subjected in the bottle capping machine.

The quantity of sealing compound applied is so chosen and it is so applied in the corner of the cap that the internal diameter of the sealing gasket is larger than (and even after deformation by being compressed upon sealing the cap on a bottle will be larger than) the diameter of the bore of the bottle neck. For a crown cap of the standard diameter of 26 mm. :a quantity of 175 to 200 milligrams'of the compound is sufficient to form the sealing gasket.

When the cap is applied to the bottle 6, as shown in FIGURE 3, the sealing gasket 5 lies opposite the upper curved peripheral surface 7 of the rim flange 8 of the bottle. The cap 1 is crimped on to the bottle by conventional capping machinery whereby the outer flared part 4 of the skirt is crimped below the rim flange, as shown in FIGURE 4, to hold the cap on the bottle, the sealing gasket 5 thereby being compressed against the curved surface 7 of the rim flange. During the crimping operation, the metal of the cap forms at the corner between the top portion and the skirt to conform more closely to the curvature of the curved part 7 of the rim flange and thereby assists in compressing the sealing gasket against the curved surface 7 of the rim flange.

The compression of the sealing gasket forces the compound both downwardly into the spaces at the upper ends of the channels formed between the internal corrugated surface of the upper end of the skirt and the opposing peripheral surface of the rim flange, and also inwardly around the top of the curved surface 7. The internal gas pressure within the bottle, which acts on the gasket as indicated by the arrows A (FIG. 4), presses the compound outwardly, and since the gasket is not stuck to the internal surface of the cap but is free to slide or slip against .the top and skirt portions of the cap, this internal pressure can move the gasket slightly to force the compound to fill the upper endsr of the channels formed by the corrugations and also completely to close any gaps between the interior of the corner of the cap and the curved surface 7 on the rim flange, thereby ensuring a gas-tight seal.

If, after the crimping operation, the cap tends to lift or dome slightly as indicated by the dotted lines in FIGURE 4 due to an increase in the internal gas pressure in the bottle, this increased internal pressure is also applied to the sealing gasket as indicated by the arrows A (FIGURE 4), and by reason of the compound not adhering to the internal surface of the cap, the pressure causes the compound. to move slightly until it is tightly compressed and compacted between the cap and the rim flange, and is forced into the corrugations, to maintain the gas-tight seal. The greater the internal pressure, the more the compound is forced into sealing compression between the cap and the rim flange. If the internal pressure in the bottle decreases, the flexure of the top portion of the cap is reduced and the cap presses the gasket more firmly against the rim flange.

The crown cap according to this invention is thus selfsealing and automatically compensating for changes of the internal gas pressure. Tests have shown that crown caps constructed as above described according to this invention, and provided with a non-adhering sealing gasket chntaining 175 to 200 milligrams of sealing compound, maintain a gas-tight seal up to a pressure of 12.0 lbs. per square inch. Similar aluminium crown caps but having the sealing gasket adhering to the cap, and therefore not possessing the self-sealing characteristics of the caps according to this inventiomcan only seal against pressures of up to about 60 lbs. per square inch.

The self-sealing property of the crown cap according to this invention enables the sealing gasket to be formed from a very small quantity of sealing compound, thus achieving economy in manufacture. As only a small quantity of sealing compound is used to form the gasket, the length of the skirt of the cap canalso be re,-

duced, thus effecting a further economy in the use of metal. 7 I

If the contents of the capped bottles are to be pasteurised or sterilised, the necessary heat treatment causes the pressure in the bottle to increase, this increased pressure forcing the sealing gasket to maintain the seal in the manner above explained. 'If the temperature of the heat treatment is suflicient to soften the compound slightly, the internal pressure will still force the compound into any gaps between the surface 7 of the rim flange and the cap, and in the upper ends of the corrugations. Upon the bottle and its contents being cooled or allowed to cool, the fiexedtop'portion of the cap 7 retracts and applies greater pressure on to the sealing gasket.

As above mentioned, epoxy-phenolic resin lacquers provide coatings to which rubberised sealing compounds, such as G485, do not adhere. The non-ad-hesive'coating may be applied directly on to the strip metal from which the cap is to be made.

When it is necessary to protect the contents of the bottle from coming into direct contact with the aluminium of the cap, it is preferred to coat the interior surface of the cap with a non-adhesive lacquer as above described before applying the sealing compound. If it be desired that such protection be afforded by a vinyl or other lacquer to which the sealing compound firmly adheres, this .adhesive lacquer is applied only over the central part 9 of the underside of the top portion of the cap within the ring 5, either directly on to the metal or as a'second coating on a non-adhesive coating. The adhesive lacquer may be applied as a circular spot on the metal cap before the sealing compound is applied and of such a size that the sealing compound does not overlie the adhesive lacquer. Alternatively, the adhesive lacquer may be applied after the sealing compound has been applied or substantially simultaneously with its application. For example, as the sealing compound is conveniently applied by squirting from a nozzle while the cap is being rotated about a substantially vertical axis and with its skirt facing upwardly, the lacquer may be applied either substantially simultaneously or subsequently by placing or dropping a dropof lacquer on to the centre of the cap, the rotation of the cap dis-v tributing the'lacquer by centrifugal force over its internal surface within the ring of sealing compound. The instant at which the drop of lacquer is applied should be so timed that the lacquer will not be distributed by centrifugal force on to any part of the corner zone which is to be covered with sealing compound before the complete ring of sealing compound has been applied." Alternatively the lacquer may be applied at a second station in the machine to which the cap is transferred after the sealing compound has been applied. The lacquer and the sealing compound may be cured simultaneously by the subsequent heat treatment.

In a modification the cap is provided with a second ring of sealing compound which is applied around the interior of the skirt as describedin United States patent application Serial No. 669,004 in such a position that this second ring of sealing compound will be compressed against the underside of the rim flange when the cap is crimped on to a bottle. This embodiment of the invention is illustrated in FIGURES 5 and 6 of the drawing, in which the additional ring of sealing compound is indicated at 10. The ring 10 of sealing compound, in contradistinction to the ring 5,must firmly adhere to the skirt so that the region of the skirt to which the ring 10 is applied must have previously been coated with an adhesive lacquer, such as a vinyl lacquer. This lacquer must not, however, extend beneath the ring 5, or alternatively must be covered, where the ring 5 is tobe applied, with a coating of a non-adhesive lacquer.

Whilst particular embodiments have been described, it

will be understood that various modifications may be made without departing from the scope of the invention. For example the ring 5 of sealing compound may extend somewhat further towards the centre of the underside of the top portion of the cap than is shown in the drawings but care must be taken that the internal diameter of the sealing gasket is greater than the diameter of the bore of the neck of the bottle, so that the gasket will not be compressed over the lip of the bore which would restrict the free sliding or slipping movement of the gasket and would prevent the internal pressure from being able to force the gasket outwardly to maintain the seal. Further, although the invention has been described with reference to a crown cap made of aluminium, the cap may be made of oth r metals, such as tinplate.

It is also to be understood that if it should be possible, by suitable compound ng and choice of ingredients, to produce other resilient sealing compounds which, when applied in the semi-liquid state, do not adhere to vinyl or other lacquers to which the sealing compounds at present commercially available firmly stick, then such lacquers, which have herein previously been referred to as adhesive lacquers, would constitute non-adhesive lacquers when used with such other sealing compounds for produc'mg crown caps according to this invention.

I claim:

1. A metal crown cap having a top portion and a corrugated skirt portion which is adapted to be crimped on to the rim flange around the neck of a bottle, said cap having an annular sealing gasket of a resilient sealing compound applied around the interior of the corner zone of the cap between the top portion and the skirt portion, wherein the compound is applied on to a coating, previously applied on the interior surface of the cap, of a material to which the compound does not adhere, the sealing gasket, the internal diameter of which is greater than the diameter of the bore of the neck of the bottle,

being held in the cap by reason of the close surface contact existing between the compound and the coating but being free to move by slipping of the compound on the coating applied over the top and skirt portions of the cap.

2. A crown cap as claimed in claim 1, wherein the coating is fiormed of an epoxy-phenolic resin.

3. A crown cap as claimed in claim 2 wherein the cap is made of aluminium.

4. A crown cap made from aluminium having a top portion and a corrugated skirt which is adapted to be crimped around the underside of the rim flange of a bottle to secure the cap thereon, the cap having a flowed-in sealing ring of a resilient sealing compound applied around the interior of the corner zone of the cap between the top portion and the skirt, wherein the compound is applied on to the surface of a coating of an epoxyphenolic resin which has been previously applied to the surface of the metal, whereby the sealing ring is held in the cap by reason of the close surface contact existing between the ring and the surface of the coating to which it is applied but is nevertheless free to slide on the surface of the coating.

References Cited in the file of this patent UNITED STATES PATENTS 2,327,454 Punte Aug. 24, 1943 2,444,978 Cooke July 13, 1948 2,463,701 Krueger Mar. 8, 1949 2,481,111 Griswold Sept. 6, 1949 2,484,039 Krueger Oct. 11, 1949 2,528,506 Foye Nov. 7, 1950 2,548,305 Gora Apr. 10, 1951 2,765,943 Woltt Oct. 9, 1956 FOREIGN PATENTS 518,183 Italy Mar. 4, 1955 

1. A METAL CROWN CAP HAVING A TOP PORTION AND A CORRUGATED SKIRT PORTION WHICH IS ADAPTED TO BE CRIMPED ON TO THE RIM FLANGE AROUND THE NECK OF A BOTTLE, SAID CAP HAVING AN ANNULAR SEALING GASKET OF A RESILIENT SEALING COMPOUND APPLIED AROUND THE INTERIOR OF THE CORNER ZONE OF THE CAP BETWEEN THE TOP PORTION AND THE SKIRT PORTION, WHEREIN THE COMPOUND IS APPLIED ON TO A COATING, PREVIOUSLY APPLIED ON THE INTERIOR SURFACE OF THE CAP, OF A MATERIAL TO WHICH THE COMPOUND DOES NOT ADHERE, THE SEALING GASKET, THE INTERNAL DIAMETER OF WHICH IS GREATER THAN THE DIAMETER OF THE BORE OF THE NECK OF THE BOTTLE, BEING HELD IN THE CAP BY REASON OF THE CLOSE SURFACE CONTACT EXISTING BETWEEN THE COMPOUND AND THE COATING BUT BEING FREE TO MOVE BY SLIPPING OF THE COMPOUND ON THE COATING APPLIED OVER THE TOP AND SKIRT PORTIONS OF THE CAP. 